After posting this, I discovered a product called PHP Chess. Website:
http://www.phpchess.com
The product costs $50, which I paid. Unfortunately the download link I paid for leads to a corrupted zip file. These kinda things annoy me.
It seems like a decent program, better than some chess. They have a free version for download and a version running on their site. I believe there's a PHPBB integration for it, but not for vBulletin.
I've decided to go with PHP Chess..... assuming I can ever get my hands on a zip file that works.